The present invention relates to a tennis racket, and more particularly relates to improvement in dynamic behaviour of a light weight tennis racket suited for use by unskilled players, in particular at off-spot shooting.
Here, the term "off-spot shooting" refers to shooting at face sections outside the sweet spot of a tennis racket.
It is already proposed to arrange a heavy mass at a section of a head corresponding to the largest width of the face of a tennis racket for higher plane stability in the case of off-spot shooting, and the mass is usually made of a material having a specific gravity larger than that of a frame of the tennis racket. For example, such a mass is made of lead or the like.
It is also proposed to arrange a heavy mass, which is made of a material of a large specific gravity such as lead, at the frame top of a tennis racket. Presence of such a heavy mass at the frame top increases the moment of inertia of area of the tennis racket and brings the center of mass near the center of the face of the tennis racket. Increased moment of inertia of area and displaced center of mass concur to assure good flight of balls even in the case of off-spot shooting.
Despite such optimization of moment of inertia and center of mass, no appreciable improvements have been attained in relation to repulsion characteristics and vibratory impact at off-spot shooting. As a result, lowering in repulsion characteristics causes low speed flight of balls and high vibratory impact tends to impose physical damages such as tennis elbow in particular on unskilled players, both in case of off-spot shooting.
In addition, presence of a heavy mass at the frame top inevitably causes undesirable displacement of the sweet spot towards the frame top. Normally, a sweet spot of a tennis racket is designed to be situated around the center area of its face. So, such displacement of the sweet spot towards the frame top reduces the effective surface area of the sweet spot because of the substantially oval shape of the face. Knowledge of this results imposes a sort of mental stress on unskilled players and makes them feel it difficult to manipulate the tennis racket as they intend.